1. Field of the Invention
The present invention relates to a CMOS image sensor and a method for manufacturing the same, and more particularly, to a CMOS image sensor and a method for manufacturing the same, in which a microlens is formed between each light-shielding layer formed in the shape of an upside-down T, thereby improving the light-reflection properties of the microlenses and protecting the microlenses during or within packaging.
2. Discussion of the Related Art
Generally, an image sensor is a semiconductor device for converting an optical image to an electric signal. The image sensor can be broadly categorized into a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor.
In the CCD, respective metal-oxide-silicon MOS capacitors are positioned adjacently, wherein electric charge carriers are stored in and transferred to the capacitors. Meanwhile, the CMOS image sensor adopts the CMOS technology of using a control circuit and a signal processing circuit as the peripheral circuit. The CMOS image sensor uses the switching method of sequentially detecting output signals by forming the predetermined number of MOS transistors in correspondence with the number of pixels.
In accordance with conventional methods for manufacturing a vertical CMOS image sensor, a light-shielding layer may be used to prevent the reflection of light. However, it is inefficient in that it necessarily requires an additional process step. Also, the microlens may be damaged during the packaging process.
Hereinafter, a CMOS image sensor and a method for manufacturing the same according to the related art will be described with reference to the accompanying drawings.
FIG. 1 is a cross sectional view of a CMOS image sensor according to the related art.
As shown in FIG. 1, a plurality of photodiodes 11 are formed in a semiconductor substrate 10. Then, a first insulating layer 12 is formed on the semiconductor substrate 10, including the plurality of photodiodes 11, and is then selectively etched to form a via-hole. After that, the via-hole is filled with a conductive material, thereby forming a contact 13. Subsequently, a metal layer is deposited and patterned on the first insulating layer 12, including the contact 13. Also, a metal line 16 is formed in a pixel region 14, and a metal line 16 and a pad 17 are formed in a peripheral region 15. Then, a second insulating layer 18 of oxide is formed and planarized on the first insulating layer 12, including the metal line 16 and the pad 17. Thereafter, a light-shielding layer (not shown) is formed on necessary portions of the second insulating layer 18.
To protect the light-shielding layer, a passivation layer 19 of oxide or nitride is formed and planarized by chemical mechanical polishing (CMP). Then, microlenses 20 are formed on the passivation layer 19, where each of the microlenses 20 is associated with a corresponding one of the photodiodes 11.
However, the CMOS image sensor and the method for manufacturing the same according to the related art have at least the following disadvantages.
When using the light-shielding layer, it is necessary to form the insulating layer for protecting the light-shielding layer, thereby causing inefficiency in the manufacturing process. Also, since the packaging process is performed on the microlenses, the microlenses may be damaged.